Difference between J and F in Vertex Edit Mode?


I am asking myself everytime what’s the difference between “Make Edge”/"Fill (Shortcut F) and “Vertex Connect Path”/“Join” (Shortcut J) to connect two vertices in Edit Mode? What function to use when? In my opinion it’s the same function, am I right?

Nope, not the same, if you select two diagonal points on a quad face and press F, you end up with a new edge between the two points which is not part of the face. Select the two points and press j and it makes the quad into 2 triangles. I use ‘j’ a lot when tidying up booleans etc to create nicer connecting edges.

Correction: you just made the quad face into two triangles

Nope, j makes 2 triangles, f creates an edge. Simple proof, create a plane, select two points diagonally, hit ‘f’. Now go into face mode, click one “triangle”, the whole face is selected. Hide that face, you are left with a single diagonal edge.

Small video proving the point in 8.2

Did not watch the video, but am quite sure f creates a new face taking chosen verts/faces into account. So if you select 3 certs, you get a triangle, select 4 and you get a quad

@mohamed_omer Thats true, but that isn’t what colkai meant.
You both are right:
F creates complete new edges/faces only considering the selected vertices. If you do this in a place where there is already geometry (a face or an edge) this will cause problems with shading and different modifiers (subsurf, bevel, …). F should only be used to fill holes or create new faces.
J connects the vertices in the order they got selected by cutting throug existing mesh. Similar to the knife tool. This only works when there are faces preexisting to cut through. This is most commonly used to generate detail where an edge Loop would not work or to clean up topology.


Thank you for the illumination

Main difference with top left and bottom right vertices selected, see attached images:

Thank you so much guys for your answers. I did a test and it proofed.
Actually, J was the function I was expecting and looking for. F is for creating new edges and faces. Visually, I couldn’t see any differences, but there are!